Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02909296 2015-10-16
LED LAMP WITH A FLEXIBLE HEAT SINK
FIELD OF INVENTION
The present invention relates generally to vehicle lights that use light
emitting
diodes (LEDs). More specifically, the invention relates to an LED lamp with a
heat sink.
BACKGROUND OF THE INVENTION
In recent years it has become popular to use LED lighting to provide
illumination
for automobiles, including especially headlights, fog lights, taillights,
signal lights, and
emergency indicators. LED lights can be superior to filament or gas bulbs in
terms of
efficiency, life span, size, directional control, light intensity and light
quality. High
intensity LED lights, especially when used for headlights and fog lights
generate a
significant amount of heat in their semiconductor junctions. This heat can
cause problems
such as melting or otherwise deteriorating the LED light itself, or its
surroundings. In
extreme cases the heat can create a fire risk.
To address the excessive heat problem, it has been known to provide fans or to
make a large body out of heavy rigid materials to disperse the heat. Fans are
not ideal
because they consume energy, take up valuable space, make noise, and tend to
wear out
before the LED lighting element. Using a large rigid body to act as a heat
sink is also
problematic because of cost and space requirements. What is needed is a
mechanism for
removing heat from semiconductor junctions without using a fan and without
using a large
rigid body.
SUMMARY OF THE INVENTION
According to one embodiment, the present invention is directed to an LED lamp
with a heat sink. The lamp includes a wire harness adapted for connection to
an electrical
system. First and second circuit boards are electrically connected to the wire
harness. The
circuit boards are mounted on opposite sides of the heat conducting member. A
first light
emitting diode is provided on the first circuit board, and a second light
emitting diode is
provided on the second circuit board. A flexible heat sink is mechanically
connected to the
heat conducting member. The flexible heat sink may be a braided metal band.
The braided
metal band may be folded into first and second loops. The flexible heat sink
may include
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CA 02909296 2015-10-16
,
a first and a second braided metal band, and wherein the first and second
braided metal
bands are crimped to the heat conducting member with the heat conducting
member
sandwiched between the braided metal bands. The braided metal band may be made
from
copper strands. The braided metal band may be made from tinned copper strands.
The heat
conducting member may be a copper bar. The circuit boards may mounted on the
heat
conducting member by a heat conducting adhesive. The circuit boards may be
mounted to
the heat conducting member with the light emitting diodes proximate to a first
end of the
heat conducting member and the flexible heat sink connected at a second end of
the heat
conducting member opposite from the first end of the heat conducting member.
The light
emitting diodes may produce at least 1100 lumens. The LED lamp may be free
from fans.
The lamp may include a mounting base, wherein the circuit boards and the heat
conducting
member are enclosed within the mounting base, wherein the mounting base has
openings
to accommodate the light emitting diodes, and wherein the flexible heat sink
extends
outwardly out of the mounting base. The electrical system may be an automotive
electrical
system, and the mounting base may be adapted for attachment to an automobile
headlight.
According to another embodiment, the present invention is directed to a method
of
installing an LED lamp into a light fixture. An LED lamp is provided that has
a light
emitting diode on a circuit board, a heat conducting member supporting the
circuit board, a
flexible heat sink made from a flexible metal fabric attached to the heat
conducting
member, and a mounting body enclosing the circuit board and heat conducting
member.
The flexible heat sink is shaped in to a desired shape to fit in a space
behind the light
fixture. The mounting body is mounted in the light fixture with the light
emitting diode on
a front side of the fixture and the flexible heat sink in the space behind the
light fixture.
The flexible metal fabric may be formed with a plurality of loops and the
shaping step may
include expanding the loops. The flexible metal fabric may be braided copper.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a LED lamp with a heat sink according to one
embodiment of the present invention.
Figure 2 is a top plan view of the LED lamp of Figure 1.
Figure 3 is a perspective view of a wire harness, circuit boards, and light
emitting
diodes used in making the LED lamp of Figure 1.
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,
,
. .
Figure 4 is a perspective view of the wire harness, circuit boards, and light
emitting
diodes of Figure 3.
Figure 5 is a top plan view of the internal components of the LED lamp of
Figure 1
with the tower body and mounting structure removed.
Figure 6 is a partial cross-section elevation view of the internal components
of
Figure 5.
Figure 7 is an elevation view of two pieces that snap together to form a tower
body
and enclosure according to one embodiment of the present invention.
Figure 8 is a perspective view of a mounting structure from the LED lamp of
Figure
1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Figures 1 and 2 show an LED lamp 10 according to one embodiment of the present
invention. The LED lamp 10 is adapted for use as a headlight in an automobile.
The LED
lamp 10 includes a tower body 12 and mounting structure 14 that permit the
lamp 10 to be
mounted on an automobile. Together the tower body 12 and mounting structure 14
provide
a mounting base that is adapted for mounting to a light fixture, such as an
automobile
headlight. The tower body 12 includes openings 16 through which light emitting
diodes 18
are provided. A wire harness 20 extends from one end of the tower body 12. The
wire
harness 20 includes a plug 22 that is adapted to interface with an LED ballast
(not shown)
that will connect to the automobiles electrical system. Also extending from
the one of the
tower body 12 is a flexible heat sink 24. The flexible heat sink 24 includes
loops 26 of a
metal fabric that can be easily deformed to fit in a variety of spaces
depending upon where
the lamp 10 is installed.
Figure 3 shows some of the internal components of the LED lamp 10 of Figures 1
and 2. The wire harness 20 includes a plurality of electrically conductive
wires 28 that are
electrically connected, for example by soldering, to two circuit boards 30.
Each of the
circuit boards 30 has two light emitting diodes 18 attached at an opposite end
of the circuit
board 30 from the attachment point of the wires 28. The two light emitting
diodes on each
circuit board may correspond, for example, with a low beam setting and a high
beam
setting when used in an automobile. Those of skill in the art will appreciate
that any
number of light emitting diodes 18 might be used beneficially in the present
invention.
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Furthermore, a single circuit board 30 may be used in some embodiments of the
invention.
The circuit boards 30 are adapted to control the light emitting diodes
according to the input
voltage provided through the wire harness 28.
In manufacturing the LED lamp 10 of Figures 1 and 2, the assembly of Figures 3
and 4 is created by soldering a wire harness 20 to the circuit boards 30. The
circuit boards
30 are available as component parts that include the light emitting diodes 18.
Various
circuit boards 30 and light emitting diode 18 combinations may be used
depending upon
the lighting requirements. In the preferred embodiment the light emitting
diodes 18 are
rated to produce at least 1100 lumens, and preferably about 2500 lumens or
more.
Figure 5 shows a top plan view of the internal components of the LED lamp 10
with the tower body 12 and mounting structure 14 removed. The circuit boards
30 are
mounted on opposite sides of a heat conducting member 32. This circuit boards
30 may be
fixed to the heat conducting member 32 by the use of a heat conducting
electrically
insulating adhesive, such as a two-part epoxy with ultra-high thermal
conductivity and
adhesive strength. In one embodiment an epoxy under the brand name Silanex
Model
#ST0903 has been found to be effective. It is important that the circuit
boards 30 be in
good thermal connection with the heat conducting member 32 such that heat
energy can be
readily transferred from the circuit boards 30 to the heat conducting member
32. The heat
conducting member 32 should be made of a material that is a good conductor of
heat, and
that is durable enough to serve as a substrate for the circuit boards 30.
According to one
embodiment, the heat conducting member 32 is made from a copper tube flattened
to have
the approximate dimensions of 3 inches X .45 inches X .12 inches with the ends
crimped
closed to prevent moisture from entering. Alternatively, the heat conducting
member could
be formed from a solid copper bar to approximately the same dimensions. Other
materials,
including especially other metals that are good heat conductors, may be used
to form the
heat conducting member.
As best seen in the cross-sectional view of Figure 6, the flexible heat sink
24 is held
in place against the heat conducting member 32 by a mechanical crimp 34. Other
fastening
mechanisms may be used as long as they allow for good thermal contact between
the heat
sink 24 and the heat conducting member 32. The flexible heat sink 24 of the
preferred
embodiment is formed from a braided flat copper cable. These braided copper
cables are
commonly used as battery ground straps. The cable may alternatively be formed
from
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braided or woven tinned copper, or other flexible metal fabrics. In the
embodiment of
Figure 6 two sections of cable, each about eight (8) inches long are used.
Each section of
the cable is folded into two loops 26 of approximately equal size with the
free ends
captured under the crimp 34.
To form the finished LED lamp 10 of Figures 1 and 2, the assembly of Figure 6
has
a tower body 12 snap fit together covering the circuit boards 30, the heat
conducting
member 32, and the crimp 34. The tower body 12 provides support for the
mounting
structure 14 that is used to attach the lamp 10 in place in a light fixture.
Furthermore, the
tower body 12 protects the circuit boards and the electrical connections from
fouling and
stresses. The tower body 12 may be formed from two heat resistant nylon molded
pieces
12a and 12b as shown in Figure 7 that snap fit together to form the tower body
12. The
tower body 12 is generally fully closed, except that openings 16 are provided
to
accommodate the light emitting diodes 18. Additionally, the end of the tower
body 12 that
is generally opposite from the diode openings 16 includes openings for the
wire harness 20
and the flexible heat sink 24.
The tower body 12 may include features near the light emitting diode openings
16
that shape the light emitted by the lamp 10. For example, as best seen in
Figure 2, a
projection 36 may be provided near the opening 16 that partially blocks a
portion of the
light emitted by the light emitting diodes 18, and especially blocks the light
from the end-
most light emitting diode 18 in one direction to shape the light beam emitted
by the lamp
10. The arrangement shown is suitable for use as a headlight lamp that
provides a low
beam and a high beam. The low beam (lower light emitting diodes) turns off and
the upper
light emitting diodes are illuminated on each side. In alternative versions
the lower light
emitting diodes will dim about 50% and the upper light emitting diodes will
turn on 100%
in high beam mode. In low beam mode the lower light emitting diodes would
still be
100% and the upper light emitting diodes will be off.
The tower body 12 may also include molded-in features that aid in mounting the
lamp 10 in place. For example, as best seen in Figure 2, the tower body 12 may
include a
mounting projection 38 that includes a wedge surface 40 that is used to draw
the lamp 10
into tight engagement with a socket in a headlight or other light fixture.
Figure 8 shows the mounting structure 14 according to one embodiment of the
present invention. The mounting structure 14 fits around the outer surface of
the tower
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body 12 and may be friction fit or adhered to the body 12. The mounting
structure 14
includes wings 42 acts as a handle or lever to aid in twisting the lamp 10
into place in a
socket of a light fixture, such as a headlight. A gasket or 0 ring (not shown)
may be
provided to seal the lamp 10 with the fixture when mounted in the socket.
When mounting the lamp 10 in a socket or other fixture space, the flexible
heat sink
24 can be molded and deformed to best fit in the available space. The loops 26
of the heat
sink 24 are preferably spread apart as much as the space permits to increase
the surface
area and to allow a greater volume of air between the loops. The ability of
the loops 26 to
take on a variety of shapes is a significant advantage for the present
invention. The metal
fabric, such as braided copper, that is used to form the flexible heat sink 24
has some
memory, but will generally retain the new shape given in deforming the heat
sink 24 to
install it. When installing the lamp 10 it is desirable to spread out the
loops 26 both in
terms of making the loops larger to increase the space between the surfaces of
the heat sink
24 and in terms of making the strand wider to increase the surface area.
In use, the heat created by the junctions of the light emitting diodes 18 will
be
transferred into the heat conducting member 32. Because the heat conducting
member 32
is made from an excellent heat conducting material, such as copper, the vast
majority of the
generated heat energy will be transferred to the flexible heat sink 24 by
conduction. The
flexible heat sink 24 relies on its large surface area to dissipate the heat
by convection and
some radiation into the space behind the light fixture. Therefore, even lamps
that produce
2500 lumens or more of light may be utilized without fans and without large
rigid bodies to
dissipate the heat energy. This allows for greater flexibility in mounting
locations, reduced
costs, greater durability, and less noise.
As used herein, the term "automobile" is used to generically refer to wheeled
motor
vehicles of all types. While the expected primary use of the invention is in
over-the-road
passenger vehicles such as cars, sport utility vehicles, and pick-ups, it is
contemplated that
the invention may be useful in other vehicles such as industrial vehicles,
over-the-road
semi-tractors, agricultural vehicles, and the like. It is also contemplated
that the LED lamp
with heat sink described herein may be useful in other applications such as
boating, home
and industrial uses.
The invention has been shown and described above with the preferred
embodiments, and it is understood that many modifications, substitutions, and
additions
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may be made. The scope scope of the claims should not be limited by the
preferred
embodiments set forth above, but should be given the broadest interpretation
consistent
with the description as a whole.
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